News National The Stats Guy: How special is your birthday? This is why some are more common than others
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The Stats Guy: How special is your birthday? This is why some are more common than others

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I always looked forward to my birthday as a kid.

Presents, cake, a little party with my friends.

What’s not to love?

It really felt like a special day.

But just how special is your birthday?

Today’s date isn’t all that special of a birthday.

June 27 is the 182nd most common birthday in Australia.

It is just as far from being the most common birthday as it is from being the most uncommon one.

What a terrible day to publish a column on birthdays in Australia!

The Australian Bureau of Statistics counted all births in Australia from 2007 to 2016 and ranked the individual birthdays from most common to least common.

The table below shows some obvious and some not so obvious patterns.

Why are some birthdays more common than others?

To explain the chart, we need to think through what needs to happen leading up to a birth. Time for some very basic and very clean sex-ed.

Let’s start at the beginning, let’s start at conception.

Over 95 per cent of Australian births are naturally conceived, we can therefore disregard IVF for now and conclude that birth spikes should be expected about 40 weeks, or 280 days, after both partners were in the same place with a bit of time to spare.

That’s more or less the length of the average pregnancy.

The five most common birthdays in Australia

Four of the five most common birthdates cluster around a fortnight from mid-September to early October.

Now let us count backwards 280 days and we arrive back at the Christmas holidays.

In late December all the stars align.

Both partners are off work, stress levels are at an all-time low (at least once the annual trip to the in in-laws is done and dusted), and it’s warm, which makes undressing an easy task.

There is a funny little outlier in our top 5 though.

The second most common birthday in Australia is April 8.

This leads us back to July 3 as a likely conception date.

What is so sexy about the 3rd of July?

A belated ritual to celebrate the end of the financial year?

A ski season induced baby peak?

I think the most likely explanation is Australians escaping winter to procreate in Europe or Bali.

Christmas in July so to speak …

The table invites us to speculate about the impact of major events on, well, let’s say our mood.

Early to mid-July are relatively rare birthdays except for July 8 and 9 which are relatively common birthdays.

Counting back 280 days, we arrive at Grand Final weekend.

Is there really a footy-induced mini baby boom every year?

I just want to believe that!

Does the Melbourne Cup actually stop the nation in early November or do young couples get busy?

The mini peak on the 5th and 6th of August suggests that the race doesn’t stop the entire nation …

The five least common birthdays in Australia

The least common birthdays are more easily explained and require less speculation.

February 29 obviously only comes around every four years.

If you are born on February 29 your birthday couldn’t possibly more special.

Congratulations, you really are special!

The other most uncommon birthdays are all public holidays.

Your baby doesn’t care much about Queen’s Birthday, Australia Day, or Christmas.

Your doctor on the other hand …

Since about 35 per cent of all births in Australia are Caesarean Sections that can be scheduled and timed to a degree, doctors tend to not book them on a holiday.

For the same reason Saturdays and Sundays are relatively uncommon days to be born on.

It’s not only public holidays that the C-section babies avoid as their birthdays: The whole of November and December are relatively quiet times in Australia’s maternity wards.

Counting backwards for 280 days we arrive in February and March.

Two month that are marked by an absence of public holidays.

Also, the workers of Australia just finished their big Christmas holidays and burned through all their annual leave.

Ultimately, the day of your birth doesn’t matter nearly as much as how you spend your day and who you spend it with.

That’s the only thing that makes a birthday really special. A big fat birthday cake doesn’t hurt of course …

Demographer Simon Kuestenmacher is a co-founder of The Demographics Group. His columns, media commentary and public speaking focus on current socio-demographic trends and how these impact Australia. Follow Simon on Twitter or LinkedIn for daily data insights.

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